NASHVILLE - The head of Tennessee's child welfare agency resigned Tuesday under scrutiny of how her agency handled the cases of children who were investigated as possible victims of abuse and neglect, then later died.

Gov. Bill Haslam announced Kate O'Day's resignation as Department of Children's Services commissioner in a news release, saying "She was concerned that she had become more of a focus than the children the department serves."

Last week the Republican governor defended O'Day's leadership, even after the agency told a federal judge it couldn't say with total certainty how many children died while in its custody.

"She has done a lot of good work in identifying longstanding problems that have hampered the department, and we will build on those efforts as we move forward," the governor's statement said. Neither he nor O'Day was answering questions Tuesday about the latest developments.

O'Day, 56, had a troubled two-year tenure, but the agency's problems predated her. DCS has been under federal court oversight for more than a decade because of problems with Tennessee's foster care system.

The agency had made steady progress since 2001 on an improvement plan that reduced caseworker load, required more training and appointed an independent monitor.

But that progress recently had stalled. At a Jan. 25 hearing in that case, the state acknowledged that outside monitors had uncovered nine child deaths during O'Day's tenure that DCS had missed. Attorneys for the foster children complained that they have no way to evaluate how DCS is caring for their clients because they are receiving almost no information.

DCS blamed ongoing problems with faulty data on a computer tracking system installed in late 2010. Repairs are under way but officials told the court it would be July before the system can sort data and prepare needed reports.

Federal Judge Todd Campbell was clearly frustrated. While he didn't mention O'Day by name, he pointed out the problems began in 2011, the same year Haslam appointed her.

"My concern is whether there is a connection between the lack of reliable data and the safety of children," Campbell said.

The department also has been battling news organizations seeking information about how DCS handled some 200 cases of children who died or nearly died between 2009 and the middle of last year.

The Tennessean, The Associated Press and 10 other news organizations sued DCS in state court in December to obtain case records. DCS contended it was keeping the records closed to protect the children's privacy. Chancellor Carol McCoy ruled last month the agency had to redact and release them.

Four of those redacted records were turned over to the court late Monday. They raise more questions about DCS performance.

In one case, a 16-year-old boy who was supposed to be in DCS custody but had been missing for several months. He died in a car crash. The car was driven by the boy's uncle, who had five different drugs in his system.

Nothing in the released files indicates how the boy escaped custody or whether DCS did anything to recover him before the fatal crash.

The records don't provide enough information to evaluate whether DCS could have done something to prevent the child from dying. Other DCS records indicate the agency's Child Fatality Review Team also hasn't been evaluating DCS performance in such cases.

According to 2012 meeting minutes obtained by AP with a public records request, most reviews didn't discuss caseworkers' actions or make recommendations for improvements.

O'Day also was criticized for ousting more than 70 executive-level employees in her two years with the agency. Other DCS problems under O'Day included legislative outrage over closing the Taft Youth Development Center to save money and long hold times for the child abuse hotline that led 25 percent of callers to hang up before they talked to a DCS employee.

She had asked for a budget increase of more than $8 million for the next fiscal year. Last week the governor announced he was seeking a $6.7 million increase for a total budget of $647 million in state and federal funding. Haslam's budget proposed to lay off 10 DCS workers and eliminate another 20 unfilled positions while hiring 62 caseworkers, investigators and attorneys and improving salaries.

As recently as December, Haslam had expressed confidence in DCS and O'Day, who previously was president and chief executive officer of Child & Family Tennessee in Knoxville.

When DCS had to reveal that it had under-reported the number of child deaths, Haslam acknowledged there were problems and appointed one of his top advisers to conduct an analysis of the agency's operations.

O'Day's resignation came less than two weeks later and one day before she was to testify at the General Assembly about DCS problems.

Haslam named Commissioner Jim Henry, the head of the Department of Intellectual and Developmental Disabilities, to serve as interim commissioner.